Thread: Whirlybirds - is 3 enough?

I've installed whirlybirds on top of lots of shipping containers and I have to say that unless the wind is really blowing I have been largely underwhelmed.
I measure a few airflows tru whirly birds and they were always much less that the flow claimed by teh manufacturers.
Your builders comment about 3 being as effective as 5 is correct because to make a real difference you will need LOTS of them.
For example I could not really tell the difference in temperature inside a shipping container between using one or two whirlybirds.
On a large shed like yours I estimate you will need at least a dozen whirlybirds to make a difference
An even then remember when there's no wind or it's is slow they won't make any real difference..
You can get almost the same effect as whirly birds by having enough openings in the roof/gables.

What you would be better off doing as well as installing plenty of openings is installing some forced ventilation - this will also help with wood dust mitigation.
This is a 3HP (single Phase) chicken barn ventilator.
While they are very effective unfortunately they are noisy.
DunsMensShed.jpg

Shade doesn't help all that much when there's a stiff searing wind coming off the interior as the air temperature will dominate the shed temperature.
In that case all whirly birds do is replace hot air from inside with hot air from the outside.

I'm at Mount Crosby, west of brissy, and built my shed in the late 90's. Mine is 9x7.5 with 2.4 walls.

1. Get it in zinc whitehaven if you can (industrial colour only) or at least the pale grey. The colour makes a huge difference. There is a table somewhere listing the thermal rating for all colourbond colours and zinc.

2. Find out what they are charging for the whirlybirds. I installed mine a couple of summers after I built and they made a tremendous difference. Prior the shed was hotter than outside consistently. After it was the same temp as shaded areas outside. Better than nothing. You are proposing a shed 3x mine (envy). I can't comment on numbers. The colour WILL make a difference.

3. Insulation. It will create thermal lag, so if you cool the shed down overnight, which requires good ventilation, it will slow heating during the day. On the other hand it will help keep it hot into the night. I insulated the cieling on my house some years back. Being me I put temp monitors everywhere prior and measured the change. It dropped the peak temp in the house 7C but kept the place warmer at night. This is foil plus glass batts. It works in the house because I have air con.

4. Windows. When my shed got robbed that's how they got in. I would not put in windows again. If you really want them put them up high make them translucent so prying eyes can't see what you have and secure them. If it were me I'd spend the money on doors.

Realise that insulation separate outside from inside. Vents and doors couple them. If the shed is hotter than outside you open up. If it's cooler you want to close it up. You need a strategy for both.

My shed is similar size to your smaller quote (16x8), and I've got two whirlybirds. I'd say they make a massive difference! But I'm in VIC where the problem is more the sun heating the tin and radiating into the shed - our ambient temperature is lower than QLD. Even when there's no wind, they're spinning like mad - heat rises and then vents out the whirlybirds. My own mezzanine (2.4ish high) is heaps hotter than the floor - so height really matters.

I fitted a solar powered whirly on my 12x8 shed and it never gets any hotter inside than it is outside - can't ask for much better than that out here. Main advantage is that they keep running when the sun is out, regardless of wind, which is when you really need the buggers running . Better still, when the temp goes below about 20 degrees, they stop, which i also brilliant out here 'cos it can bloody chilly in the middle of winter on desert uplands.

"Your builders comment about 3 being as effective as 5 is correct because to make a real difference you will need LOTS of them." Yeah this seems to be the wisdom.

We are blessed in that there is usually a gentle breeze. We are in a valley with the only significant trees down by the creek, and so I think the hot air is channeled up the valley in the afternoons. It feels a little bit cooler in the hot afternoon standing outside on our land than you expect. I don't know if this is always enough to move the whirlybirds but we have more chances of success than a lot of people.

The Colourbond roof is not white. We have a covenant and they have asked us to colour match the house roof which will be "Gully". This is a sort of grey green colour. I can make the walls an off white - like 'surfmist'.

I suffer from vertigo. Any roof issues and I have to pay someone to look at it so the idea of a fan on the roof is unappealing. However I could install a fan at the gable end where the mezzanine will be. The other end will have 3 roller doors so when they are open basically that entire gable end is open and faces West. Although I don't know if I want those 3 doors open all the time because they also face the street.

I have planned 7 or 8 windows plus up to 2 glass doors. So you are freaking me out a bit. However where we are is a low crime area. There are only 3 roads out of town and we are at the end of a long dead end street. A street where a lot of us know each other by sight. Anyone acting suspicious tends to get a mention in a facebook group. Plus I have cameras and 2 dogs. A closed gate. In addition I work from home. Eventually in the rear part of the shed. So although they can break in, their chances of getting away with it are not high. Of course there is always the exceptionally stupid person who will try anything but hopefully I don't need to stress about that risk.
In any case, like a lot of modern houses, if the new house had any more glass we could start a cannabis operation in it. So I don't think I need to stress about windows in the shed too much.

Originally Posted by TTIT

I fitted a solar powered whirly on my 12x8 shed and it never gets any hotter inside than it is outside - can't ask for much better than that out here. Main advantage is that they keep running when the sun is out, regardless of wind, which is when you really need the buggers running . Better still, when the temp goes below about 20 degrees, they stop, which i also brilliant out here 'cos it can bloody chilly in the middle of winter on desert uplands.

I can believe the solar powered whirlies work well, not only because they don't rely on wind, but supposedly, but if we can believe the manufacturers blurb (doubtful), they move about 5 to 7x more air than regular whirlies. The one problem I can see is that if you work in the late arvo or evenings or when there's no sun they're not going to do much.

I wonder what the economics of a couple of solar panels and a bunch of low power extractor fans would be versus solar powered whirlies.

FWIW for my shoebox (42m^2) shed ventilation I have 2 very quiet squirrel cage fans, one in the middle of the shed driven by a 1/4HP motor and the other, driven by a 1/3 HP motor, also acts as a welding/spray booth extractor. Combined extraction is close to 5000 m^3/h and then if needed I can fire up the 4HP dust extractor for another 2000 m^3/h. However, I only usually run the fans for cooling if necessary in the morning for a few minutes to remove any residual hot air before switching to AC powered by solar on the house.

Originally Posted by BobL

I wonder what the economics of a couple of solar panels and a bunch of low power extractor fans would be versus solar powered whirlies.

Hey yeah!! This would be right up my alley. The problem is that I suffer from vertigo. So I wouldn't be climbing up there to install or maintain it. I sure like the concept though.

The plan is to have the whole solar array for house and shed on the roof of the shed. Half of the gable roof is orientated to face NNW so its perfect. I'm not sure how many m2 those panels are but I'm sure there will be a little space for more up there.

Someone earlier mentioned that the solar panels might have an effect like a tropical roof. I had not thought about that before. I don't know what the gap between the solar panels and the metal roofing is. Even if it is not much perhaps it would still have a significant effect. I think is an excellent point that I had not considered.

if you want windows what's to stop you placing some sort of barrier to exclude any one who is looking for a bargain.

Originally Posted by DaveVman

\Someone earlier mentioned that the solar panels might have an effect like a tropical roof. I had not thought about that before. I don't know what the gap between the solar panels and the metal roofing is. Even if it is not much perhaps it would still have a significant effect. I think is an excellent point that I had not considered.

Don't forget It also works the other way.

We have 14 panels on our corrugated iron front veranda and were told the same thing and was looking forward to having a slightly cooler outside spot to hang out outside on hot evenings. If theres no breeze there does seem to be a small difference during the day (hard to tell) but on really hot days once those hot easterlies start up early everything heats up to air temperature anyway and the roof re-radiates heat downwards like a dozen 2kW bar radiators. In the late afternoons/evenings when the sun goes down if there's no sea breeze that roof continues to radiate heat for some time afterwards and it seems to stay hotter for longer. My take is that the panels act like insulators and reduce the cooling-off effect.

You can get second hand solar panels for $10 each. When they get damaged insurance companies get the whole lot replaced so there are heaps of perfectly good ones around for next to nothing. If you get a system with an overspec inverter/charge controller (if batteries) you can increase your solar array cheap.

Solar panels are black. They get hot. There is enough of an air gap but the rails run transversely usually so you don't get good air flow to flush the hot air under the panels.

It doesn't matter if you have cameras. The builders next door gave the police their number plate when some junkies from Ipswich came up here and robbed my house, and one got charged. Slap on the wrist. It wasn't her first time. Courts don't do anything and you don't get your stuff back. Personally I'd like to rig man traps but they are illegal and with my luck they'd gaol me...

Bars, security screens, deadlocks. Make it hard for the b!@#$%^&*

I wish I'd got higher walls. More storage, easier to maneuver long objects and a tremendous reduction in radiated heat from the roof. Do get a quote. I was surprised at how little it would have cost.

Brisbane is actually less hot than Sydney. The problem up here is humidity. Some years back I flew to sydney to see my great aunt before she passed. I spent the morning by her bed then went to get lunch. About 45 minutes walk each way, 44C. I was in black long sleeve shirt trousers and shoes. Not a problem. Here it hits 30C and I'm laying on the floor under the air conditioner gasping like a gold fish that's flipped out of it's tank. Thus you might try and strategy of closing and insulating the shed and running a dehumidifier. I don't know what they cost but it'd make the space a lot more comfortable.

Just some thoughts for you to consider. If I move I will do the shed differently to address some of the mistakes I made this time, but overall it's been good.

I put whirlybird birds in my shed, I found them to be a total waste of time and money. They made no noticeable difference and didn’t take that long before they were banging and clanging as they spun.

I removed one and replaced it with an evap air con, the others I disabled to stop the racket. Would never waste money on them again.

Cheers Andrew

Originally Posted by AJ.

I put whirlybird birds in my shed, I found them to be a total waste of time and money. They made no noticeable difference and didn’t take that long before they were banging and clanging as they spun.

I removed one and replaced it with an evap air con, the others I disabled to stop the racket. Would never waste money on them again.

Cheers Andrew

A half decent evap AC will move about 10X what a whirlybird can move (when the wind is blowing hard). They are also VERY effective against fine dust. I've monitored dust levels at the mens shed (WW area ~140m^2) especially when some eedjet forgets to turn on the DC and makes a heap of dust. The Evap AC fan takes about 3-4 minutes to flush the dust down to acceptable levels. They now leave it on all the time - even in winter they leave it on low - helps with Covid too

I recently built my 6x6 shed with a single whirlybird and I’m already regretting it. I’m doubtful of any cooling effect it may provide when I could just upon the doors and windows and take advantage of the prevailing breeze. Plus I get small leaves falling in through the whirlybird gap and getting on my car

I now wish I’d left the roof closed up because I want to air condition the shed. It’s fully insulated with Insulshed 50 + acoustic batts on the walls, but that doesn’t do much against the humid Brisbane summer!

OMG! I'd love to be able to air con the shed!! In fact there is a 3 x 4.5m area that I could close off in the future to make that possible. But no way I could afford to air con the whole shed.
Evap coolers are not an option for me here in Brisvegas. It would probably makes things worse actually.
I hear what you are saying about the height. My eves are at 3.5m. This is a problem for the mezzanine store and also for any stairs up to it. However apparently there is a cost jump if we raise the eves above this.